Exercises for improving posture

I want to improve my posture. I already do crunches and such when I train, but I want to start exercising my back more. I heard that your back should be stronger than your abs if you want a good posture.

I used to do normal back extensions on the floor, but now I've started to do them while holding some light dumbbells in my hands. Is this a good exercise?

I've also been doing shoulder presses for as long as I can remember, but that doesn't do much for your back. Should I start using the reverse fly machine or something similar for my upper back?

I want to improve my posture. I already do crunches and such when I train, but I want to start exercising my back more. I heard that your back should be stronger than your abs if you want a good posture.

I used to do normal back extensions on the floor, but now I've started to do them while holding some light dumbbells in my hands. Is this a good exercise?

I've also been doing shoulder presses for as long as I can remember, but that doesn't do much for your back. Should I start using the reverse fly machine or something similar for my upper back?

First - do you have any lower back pain? If not, then you can go ahead with almost any exercise without contraindication. Often, poor posture is a result of weak abdominal muscles, or tightness of the hamstrings and the spinal erectors. Work on your abs, and stretch, especially your hamstrings, every day. Poor standing posture is also often related to spending long amount of time sitting with poor posture. If you're doing this, I'd consider buying a new ergonomic chair, or even a stool often improves sitting posture.

I have minor scoliosis. I know it can be boring but i practiced tai chi for a couple years and when they x rayed me later it had fixed itself 40 degrees. It's possible it had nothing to do with the tai chi, but i would mark that as the reason. It makes you stand upright and relaxed no matter what youre doing(at least while you're a beginner). You could just always remind yourself to stand straight.

A tight chest can contribute to rounding your shoulders forward, so stretch that it out or at least investigate. Tight traps and neck muscles can also contribute to bringing your shoulders up and "wearing them like earmuffs".

Constantly remind yourself about your posture throughout the day, little cues on the desk or in the car can help. According to my physical therapist it takes about 2 weeks of consistent posture monitoring for it to become natural.